This invention relates to silver halide color photosensitive materials used in forming full color images by exposure to near infrared light and color development processing.
The color photosensitive materials which have been widely used in the past are photosensitive to visible light and so they must be shielded from visible light during handling, for example, while being developed and processed in a dark room. This is very inconvenient in that it has been essentially impossible to visually observe the processing situation.
On the other hand, photographic materials comprising a support having thereon at least three layers (i.e., silver halide photosensitive layers) which contain silver halide emulsions which have been spectrally sensitized so as to be photosensitive to the near infrared light which is emitted from semiconductor lasers or light emitting diodes, and color couplers for colored image forming purposes, as well as methods for forming colored images by color development processing after subjecting these materials to a scanning exposure using three types of light beam with different wavelengths, have been disclosed in recent years. Examples of these materials and methods have been disclosed in JP-A-63-197947, JP-A-62-295048, JP-A-61-137149, JP-A-55-13505, U.S. Pat. No. 4,619,892 and European Patent 0,183,528A2. (The term "JP-A" as used herein signifies an "unexamined published Japanese patent application".)
Even though each of the photosensitive layers employed in these photosensitive materials have been spectrally sensitized to the infrared region, the spectral sensitivity in the visible region is still quite high. This is a general phenomenon which cannot be avoid and which is based upon the fact that the absorption bands of spectrally sensitizing dyes are wide with the edges of the absorption band extending over a wide range on the short wavelength side of the peak wavelength of the spectral absorption. Hence, photosensitive materials which have been spectrally sensitized to three different wavelengths in the infrared region must still be handled under very dim safe-lighting and they also must be processed in a state of darkness for safety. These requirements make the use of these materials disadvantageous particularly in the area of operability. Hence, an improvement that allowed these materials to be handled under bright safe-lighting in what is called a light room would be desirable from the operability viewpoint. However, the handling of photosensitive materials which have peak spectrally sensitized wavelengths of more than 670 nm under safe-lighting of the light room type is very difficult for the reasons outlined above. Accordingly a choice has to be made between using those materials which can be handled in bright safe-lighting but which are of low sensitivity and require very bright exposures of long duration, and those materials which must be handled under dark safe-lighting but which have a high sensitivity and can be used with short exposure times. However, the material must have a high sensitivity in those cases where a scanning exposure of a large image must be carried out in a very short period of time using i.e., semiconductor lasers or light emitting diodes as light sources. Hence, there is a need for sensitive materials which have an adequately high photographic speed with respect to near infrared light sources but which have a photographic speed with respect to visible light so low that it can be effectively disregarded.